082 In vivo tracking of clonal dynamics shows three phases of UV-induced skin carcinogenesis

We hypothesize that skin cancer emerges from a combination of mutations and tissue disruption. characterize clonal dynamics transcriptional signatures during carcinogenesis using lineage tracing. For 3 months, we UV-irradiated fluorophore expressing K14Cre-ERT2 Confetti mice. Clone volumes were computed 3-D digitized confocal z-stacks. scRNAseq was used to compare UV-exposed (EXP) epidermis, non-exposed (NON), tumors. Over 6 months the UV initiation, generated 914 serial images EXP/NON skin. analyzed 16,135 clones EXP 21,506 NON Median clone size did not differ between treatments change with time. However, mean 50% larger than ones, >6-fold increase in variance. The number large increased dramatically by 3-4, plateauing at 5-6. epidermis tumors revealed 16 clusters corresponding different differentiation states. observed dynamic changes when progressing normal chronically exposed skin, then Development preceded high penetrance mutations. associated expression cystatins (Scfa 3, BC100530), alarmins/proliferative keratins (Krt16, Krt6a). Flr-expressing keratinocytes exhibited altered keratinocyte differentiation, inflammation, upregulation metabolic regulators. These results show an initial disruption (2-3 months) permitting emergence unusually (phase 1), followed inter-clonal competition mutational buildup 2) lesions 3).